Your argument is flawed because of the below reasons.
When we all decide to HODL I think the markets will go down and the green markets we want will never com.
The above is not true.. If x amount of people are invested in bitcoin, and they all decide to HODL, the price will remain stable until more supply is created.. Till the time supply is fixed, and everyone is HODLING, the demand is neither increasing nor decreasing against a fixed supply... Now, you might argue that bitcoin supply will increase with time.. To counter that supply you will also have to take into consideration that there will always be some newbee somewhere in the world who would want to buy into bitcoin , thereby increasing the demand...
I think we can at the same time SELL and BUY to keep our greatest cryptocurrency alive. I stand to be corrected and also we can add some to it as to what will happen.
You can buy and sell to gain profit for yourself, but lets understand that bitcoin will not rise in value because of your buying or selling.. Bitcoin is a network ! And when do networks become more valuable? When more and more people join the network.. Think for example about a mobile phone. If only one person has a mobile phone in this world, will that phone be valuable ? No... Why? because he cannot call anyone from his phone ! Suddenly if one more person buys phone, now that the value of your phone suddenly increases because now you can make a call to the person who just bought a mobile phone... Increase this number to the number of people on the network (having mobile phone), and you realize that value of the network lies in the number of using deciding to stay on the network (HODLING) !
If you have any questions, let me know.. I give one on one bitcoin consultations too :p